1. Field of the Invention
The present invention relates generally to a method for manufacturing a semiconductor chip package and, more particularly, to a method for manufacturing a semiconductor chip package including a screen printing process.
2. Description of the Related Art
Semiconductor chips having integrated circuits may be provided as semiconductor chip packages for protection from the external environment, easy mounting and improved operational reliability. As package assembly techniques develop, semiconductor chip packages may move toward miniaturization. Various types of semiconductor chip packages have been introduced, some of which may be of a reduced size.
FIG. 1 is a cross-sectional view of a typical semiconductor chip package, for example a wire bonding ball grid array (WBGA) package.
Referring to FIG. 1, the semiconductor chip package 10 may include a semiconductor chip 11 and a substrate 15. The substrate 15 may have a window 18. The window 18 may be provided in the center of the substrate 15. The window 18 may penetrate through the substrate 15. The semiconductor chip 11 may be mounted on the substrate 15 by an adhesive 19, such that bonding pads 12 of the semiconductor chip 11 may be exposed through the window 18. The bonding pads 12 of the semiconductor chip 11 may be electrically connected to substrate pads 16 of the substrate 15 by bonding wires 21.
An encapsulant, including a first encapsulant 23 and a second encapsulant 25, may seal the semiconductor chip 11, the bonding wires 21 and a connection portion between the semiconductor chip 11 and the substrate 15. Ball lands 17 may be provided on the surface of the substrate 15. Solder balls 27 may be provided on the ball lands 17 as external connection terminals. The semiconductor chip 11 may be electrically connected to the solder balls 27 by the bonding wires 21, the substrate pads 16 and metal wirings (not shown). The solder balls 27 (and thus the semiconductor chip 11) may be electrically connected to an external substrate. The substrate 15 may include a tape wiring substrate, a printed circuit board, or have some other alternative form as is well known in this art.
Semiconductor chip packages, such as WBGA, FBGA and LOC packages for example, may have a semiconductor chip oriented such that the bonding pads may face toward and be exposed through the substrate. To manufacture such semiconductor chip packages it may be difficult to implement an epoxy dotting method in a die attaching process. Thus, some assembly techniques have been developed that employ a sheet type adhesive. However, sheet type adhesive may be relatively high-priced, which may increase the cost of manufacture. Recently, a screen printing method has been employed that may reduce the cost of manufacture.
In the screen printing method, a mask having through holes may be placed on a substrate and an adhesive may be squeezed (or pressed) into the through holes by a squeezing mechanism. As is well known in this art, the thickness and the shape of the adhesive may be adjustable.
FIG. 2 is a block diagram of a conventional method for manufacturing a semiconductor chip package.
Referring to FIG. 2, the conventional method for manufacturing a semiconductor chip package may involve a screen printing process 301, a die attaching process 302, and a curing 303 process. During the screen printing process 301, a thermosetting adhesive having a given viscosity may be applied on a substrate. During the die attaching process 302, a semiconductor chip may be provided on the adhesive. During the curing process 303, the thermosetting adhesive may be cured. Subsequently, a wire bonding process and a molding process may be performed.
Although the conventional method for manufacturing a semiconductor chip package may generally provide acceptable results, it is not without shortcomings. Some shortcomings may relate to the viscosity of the adhesive. On the one hand, if the viscosity of the adhesive is too high, the adhesive may have reduced printing capability and/or performance. For example, it may be difficult to press the adhesive through the mask. On the other hand, if the viscosity of the adhesive is too low, the adhesive may induce procedural faults. For example resin may bleed out (or flow to unintended areas of the substrate) after the screen printing process and/or resin may overflow during a die attaching process, thereby degrading the operational quality of the adhesive. The physical properties of the adhesive may influence operational quality and/or performance of the adhesive. An adhesive used in a screen printing process should have suitable viscosity in consideration of quality and/or performance. In practice, the conventional method for manufacturing a semiconductor chip package including a screen printing process may have limitations in meeting the demand for operational quality and/or performance of the adhesive.
The curing process 303 may involve loading a plurality of packages into an oven to cure the packages at the same time. Here, curing quality faults may occur due to the difference of temperature distribution according to the load quantity and position of the package within the oven.
The curing process 303 may be performed using an oven at low temperature over a long time period, thereby requiring a substantial amount of time. The die attaching process 302 may proceed using magazines, thereby costing significant production downtime. For the reasons set forth, the curing process 303 may not start promptly when the die attaching process 302 is completed. This may lead to a different point of time of cure for each material, thereby causing reduced reliability of a semiconductor chip package.